There are various lighting devices in the world, such as an illumination device for a house and a headlight for a vehicle. Detection of an abnormality of these lighting devices is performed mainly by human visual checking. However, it is difficult to recognize, by human visual checking, a subtle change in light during on state of a lighting device. Therefore, it is difficult to detect an abnormality of the lighting device by human visual checking before the lighting device breaks down, and thus, it is also difficult to replace the lighting device before the lighting device breaks down.
Japanese Patent Laying-Open No. 2007-265287 (PTL 1) discloses a monitoring system configured to detect an abnormality of an LED (Light Emitting Diode) illumination device. The monitoring system includes a camera and an LED illumination device. According to the monitoring system, an abnormality of the LED illumination device can be detected by recognizing a luminance of a particular character pattern photographed with the camera when the LED illumination device emits light.